New York Community Bancorp, the city's leading multifamily-property lender, fell by 6% today, and its stock has lost 11% since mid-May as proposed revisions to rent regulation gained steam. Signature Bank shares lost 4% today. Dime Community Bancshares, Flushing Financial and Investors Bancorp also lost ground.

All these banks have profited in the past decade by surfing the ever-rising real estate wave. At Signature Bank, New York apartment loans account for 42% of all loans, according to Wedbush Securities. Analysts say a strong majority of New York Community's and Dime Community's apartment loans are to rent-regulated properties in the city, though the banks don't provide specifics.

In any case, the rent reforms are expected to constrain net operating income, or NOI, generated by properties. Over time that could erode their value, which in turn could slow the torrid loan growth that lenders to these properties have enjoyed for many years.

Albany's reforms, which Gov. Andrew Cuomo has pledged to sign, "certainly mark a very sharp and disappointing difference to the operating environment from the past 15 years," Keefe Bruyette & Woods analysts wrote in a note to clients today, adding the changes will "meaningfully limit the growth and appreciating value of this asset class."

That said, bankers and landlords have anticipated for a while that Albany would change the rules governing rent-regulated apartments.

"Rent control is a risk, just like climate change," Mark Parrell, chief executive of property owner Equity Residential, said in a conference call earlier this year. "We've managed that risk very well."

Domenick Cama, president of Investors Bancorp, told investors earlier this year, "We don't anticipate declines in NOI going forward, just a deceleration of the increases in potential NOI going forward."

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